Wireless communication systems are widely deployed to provide, for example, a broad range of voice and data-related services. Typical wireless communication systems consist of multiple-access communication networks that allow users to share common network resources. Examples of these networks are time division multiple access (“TDMA”) systems, code division multiple access (“CDMA”) systems, single-carrier frequency division multiple access (“SC-FDMA”) systems, orthogonal frequency division multiple access (“OFDMA”) systems, or other like systems. An OFDMA system is adopted by various technology standards such as evolved universal terrestrial radio access (“E-UTRA”), Wi-Fi, worldwide interoperability for microwave access (“WiMAX”), ultra mobile broadband (“UMB”), and other similar systems. Further, the implementations of these systems are described by specifications developed by various standards bodies such as the third generation partnership project (“3GPP”) and 3GPP2.
As wireless communication systems evolve, more advanced network equipment is introduced that provide improved features, functionality, and performance. A representation of such advanced network equipment may also be referred to as long-term evolution (“LTE”) equipment or long-term evolution advanced (“LTE-A”) equipment. LTE is the next step in the evolution of high-speed packet access (“HSPA”) with higher average and peak data throughput rates, lower latency and a better user experience especially in high-demand urban areas. LTE accomplishes this higher performance with the use of broader spectrum bandwidth, OFDMA and SC-FDMA air interfaces, and advanced antenna methods. Uplink (“UL”) refers to communication from a wireless device to a node. Downlink (“DL”) refers to communication from a node to a wireless device.
A relay node (“RN”) can be used in a wireless communication system to, for instance, extend signal coverage. Further, an RN can improve overall system capacity by cooperatively transmitting, receiving or both a signal for a wireless device. For example, an RN can improve the DL system capacity by cooperatively transmitting a DL signal concurrently with a base station such that signal reception at the wireless device is improved. Similarly, an RN can also improve the UL system capacity by cooperatively transmitting an UL signal concurrently with a wireless device such that signal reception at the base station is improved.
In a typical RN deployment, a DL signal transmitted from a base station may be re-transmitted by one or more RNs before reaching a wireless device. Because of the one or more re-transmissions involved in getting the DL signal to the wireless device, latency such as packet delay may increase. Increased packet delay is important in, for instance, hybrid automatic repeat request (“HARQ”)-enabled real time applications, such as voice over internet protocol (“VoIP”), video streaming and video conferencing. For such time-sensitive applications, increased latency may result in decreased quality of service (“QoS”), loss in frame synchronization or other impairments. Therefore, a relay node-based wireless communication system may improve system coverage, system capacity or both but may adversely affect system latency. This disclosure provides methods, devices and systems for reducing such latency associated with DL transmission in a wireless communication system using RNs.